Manganese deposition control



Oct. 24, 1944. M, LEUTE ETAL 2,361,143

MANGANESE DEPOSITION CONTROL Filed Dec. 28. 1940 ANOLYTE- /Z0 FEED VCATHOL yr:

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Patented Oct. 24, 1944 UNITED STATES PATENT OFFICE 2,381,143 MANGANESEDEPOSITION OONTROL Karl M. Lente, Minneapolis, Minn., Charles L.Mantell, Manhasset, N. Y., and William L. Hammerquist, Knoxville, Tenn,assignors to Electro Manganese Corporation, Minneapolis, Minn., acorporation of Delaware Application December 28, 1940, Serial No.372,038

20 Claims. (01. 204-105) This invention relates to the electrowinning ofmanganese from its ores and other manganese containing substancescapable of yielding a solution of manganese which may be electrolyzed.

The commercially successful electrowinning of manganese by electrolysisas compared with the old method of thermal reduction possessesadvantages so important that the attainment of success is an achievementgreatly to be desired. Some of the advantages are the utilization of lowgrade ores, low cost of production, the production of manganese in sucha pure condition that its field of usefulness is greatly extended andthe production of new alloys unobtainable with the less pure manganeseobtained by thermal reduction.

Serious problems have however been encountered in attaining this successand it is the object of this invention to solve some of those problems.

The nature of those problems will now be described.

The principal electrolytic changes occurring in a solution of amanganese salt, e. g., manganese sulfate, are the following:

As shown by these equations, the manganese sulfate is split intomanganese ions and sulfate ions and water is decomposed into hydrogenand hydroxyl ions. At the cathode manganese is deposited as metallicmanganese in accordance with Equation 2 and hydroxyl ions (alkali) andhydrogen gas are formed according to Equations 3 and 4. At the anodehydrogen ions and oxygen are formed according to Equations 3 and 5. Thusthe catholyte increases in alkalinity and the anolyte increases inacidity. Since an ammonium salt, e. g., ammonium sulfate, is desirablyused as a stabilizer, alkali is also generated at the cathode inaccordance with the equations Since manganese will not deposit if theacid concentration is too high, it is necessary to segregate thesolutionat the anode from that at the cathode to prevent the acidgenerated at the anode from mixing with the solution at the oathode.This is done by means of a permeable membrane called a diaphragm whichdivides the cell into two compartments called the anolyte and catholyte,respectively.

Thus, the principal products are metallic manganese, sulfuric acid,hydrogen gas and oxygen gas. The sulfuric acid is utilized to dissolvefresh ore and remains in the electrolyte, taking part in a cycle asfollows:

Thus the output is metallic manganese, hydrogen and oxygen and the inputis manganese ore, water and electricity. The electrolyte, as a whole,remains as a body, to which manganese oxide is added and from whichmetallic manganese, hydrogen and oxygen is removed. Thus input andoutput is shown as follows:

The manganese ore is dissolved by acid anolyte liquid and the solutionis purified as much as possible before feeding it to the cell. Howeverit is never practically possible to remove all traces of impuritiesprior to introducing the solution to the cell and because theelectrolyte as a whole remains as a body of liquid to which thedissolved and purified manganese is continuously added, traces ofimpurities build up cumulatively and by contamination of the manganesedeposit, tend to thwart one of the basic purposes of the electrowinningprocess, 1. e., the production of metallic manganese in an extremelypure condition. This is one of the problems solved by the presentinvention.

Prior to the present invention the process employed in an attempt toproduce manganese commercially by the electrowinning method may besummarized as follows:

The electrolytic cell consisted of a series of cathodes and anodesarranged in alternate and spaced relation and separated by diaphragmsthus forming a plurality of anolyte and catholyte chambers, manifoldedrespectively so as to provide in effect a single anolyte and a singlecatholyte chamber separated by a diaphragm but much more compact thansuch arrangement having an equivalent volume and electrode area.

In using this apparatus, the anolyte was withdrawn from its chamber andmixed with ore to Gen rate catholyte liquid which was fed to the It wasdiscovered that during electrolysis it is of vital importance tomaintain a minimum critical cathode potential drop, that the lack ofuniformity in results was attended by changes in the cathode potentialand that by controlling this potential, e. g., by varying the over-allvoltage enough to maintain a constant cathode drop, that satisfactorydeposition could be obtained, as set forth in the copending applicationof Charles L. Mantel], Serial No. 401,893, filed July 11, 1941, issuedas Patent No. 2,286,148 on June 9, 1942.

The source of the variations in cathode drop were traced to variationsin factors influencing the various resistances in the cell. Thosefactors include the composition and pH of the electrolyte, i. e., theanolyte and catholyte.

As above explained, the deposition of manganese at the cathode causes adepletion of the concentration of manganese salt in the catholyte andthe generation of acid at the anode causes an increase of acidconcentration (decrease of pH) in the anolyte. These changes cause theresistance (or conductivity) of the said electrolytes to change andconsequently, when operating with a constant over-all cell voltage,changes the cathode potential since the latter is the difference betweenthe over-all cell voltage and the voltage drops at points in the systemother than at the cathode.

It has been discovered that if the concentration and pH of catholyte andanolyte are controlled within certain limits, that the resistances andpotential drops of these solutions will also be controlled, that thismakes possible a maintenance of the proper cathode potential at aconstant over-all cell voltage and proper control of manganesedeposition over the long operating periods necessitated by successfulcommercial operation.

It is therefore an object of the present invention to control thecomposition of the catholyte and anolyte within prescribed limits and tothereby control the resistances of these liquids, to make possible theattainment of satisfactory manganese deposition over long periods oftime by providing means of controlling the cathode potential drop.

It is a further object to provide an improved process and means ofcontrolling the composition of catholyte and anolyte within any desiredlimits.

It is a further object to avoid the contamination of the manganesedeposit caused by the cumulative build-up of small proportions ofimpurities introduced into the electrolyte by purified manganesesolutions.

In accordance with this invention the concentration of manganese in thecatholyte, the pH of the catholyte and the pH, of the anolyte arecontrolled within certain preferred prescribed limits. In addition thetemperature of the catholyte and anolyte are likewise preferablycontrolled. This is preferably accomplished by employing recirculationof the catholyte and anolyte, respectively, as hereinafter more fullyexplained. Furthermore, the recirculated catholyte or anolyte or bothare not only continuously recirculated but also continuously purified.

tween the electrodes at a density sumcient to remove manganese from thecatholyte and deposit it on the cathode at a predetermined rate in termsof grams per liter per minute, which may, for example, be from 0.25 to2.00 grams of manganese per liter per minute. As above explained, thiselectrolytic deposition causes an increase in acidity in the anolyte,that is to say, the generation of hydrogen ion in the anolyte at apredetermined rate in terms of hydrogen ion per liter per minute, orexpressed otherwise, a depletion of hydroxyl ions in the anolyte at acorresponding predetermined rate. At the same time the alkalinity at thecathode increases, that is to say, the pH of the catholyte increases.There are therefore three important changes which occur:

1. Loss of manganese in the catholyte;

2. Increase of pH in the catholyte;

3. Decrease of pH or increase of acid concentration in the anolyte.

In accordance with the present invention the changes in these variablesare controlled within prescribed limits, as already stated, this beingpreferably accomplished by e ploying recirculation as a means to thatend.

In respect to the control of concentration of manganese in thecatholyte, in accordance with a this invention anolyte liquid iswithdrawn from Current is passed through the electrolytes be- 7 theanolyte chamber, replenished with manganese and there is continuouslyfed to the catholyte chamber catholyte feed liquid having apredetermined maximum concentration of manganese in the form of asoluble salt thereof (which may, for example, be manganese sulfate),thus establishing a main circulation stream. As a result of electrolyticdeposition of manganese from the catholyte chamber the concentration ofmanganese as soluble salt in the catholyte liquid decreases and there iscontinuously withdrawn from the catholyte chamber catholyte liquidhaving a lower concentration of manganese than that of the catholytefeed liquid. The concentration of manganese in the catholyte withdrawnfrom the catholyte chamber is then restored approximately to theconcentration of manganese in the catholyte feed, this being preferablyaccomplished by the addition of liquid having a high concentration ofmanganese obtained by digesting a suitable ore or other manganesecompound with anolyte liquid. The liquid withdrawn from the catholytechamber and thus restored to the concentration of the catholyte feedliquor is then returned to the catholyte chamber, as feed liquortherefor, and is thereby recirculated in shunt-wise relation to the maincirculation stream and the recirculation is effected at a ratesufllcient to maintain in the liquid withdrawn from the catholytechamber a predetermined minimum concentration of manganese. By thismeans the concentration of manganese in the catholyte liquid ismaintained between predetermined fixed limits. This rate is dependentupon four factors:

(a) The rate of deposition of manganese;

(b) The rate of removal of catholyte liquid which may be caused bypassage thereof into the anolyte liquid or withdrawal of the catholyteliquid and addition thereof to the anolyte;

(c) The concentration of the catholyte feed liquid; and

(d) The concentration of the liquid withdrawn from the catholyte chamberand recirculated.

To illustrate the relationship of these factors let it be assumed by wayof example that the catholyte liquid is depleted of manganese at therate of 2 grams per liter per minute, most of this being caused by-thedeposition of manganese on the cathode and the remainder by transfer ofcatholyte liquid to the anolyte liquid. Therefore (a) +(b):2. Let it beassumed that the concentration of manganese in the liquid led to thecatholyte chamber is 35 grams of manganese per liter. Let it also beassumed that it is desired to maintain the concentration of manganese inthe liquid withdrawn from the catholyte chamber at a predeterminedminimum of 34 grams of manganese per liter. It will then be necessarynot only to restore the concentration of manganese in the liquidwithdrawn from the catholyte chamber to about 35 grams per liter butalso to maintain the said recirculation at a rate of 2 liters per minutefor each liter of catholyte solution. Therefore the equation todetermine the rate of recirculation is as follows:

Rate of recirculation=(a) +(b) +(c) -(d) From this it will be clear thatas the difference between the manganese concentration in the catholytefeed liquid and the liquid withdrawn from the catholyte chamberdecreases, the rate of recirculation in shunt-wise relation to the maincirculation stream must correspondingly increase in accordance with saidequation.

The preferred range of concentration of the manganese in the catholytefeed liquid is about 25 to 50 grams of manganese per liter in the formof a soluble salt thereof and the maximum difference in concentrationbetween the liquids fed to and withdrawn from the catholyte chamber isabout grams per liter.

Applying the same principle to the control of pH in the catholyteliquid,. the catholyte feed liquid is maintained at a predeterminedminimum and the liquid withdrawn from the catholyte chamber necessarilyhas a higher .pH because of the electrolytic changes occurring in saidchamber. The pH of said liquid withdrawn from the catholyte chamber isthen reduced to approximately that of the catholyte feed liquid andreturned as feed liquid to said catholyte chamber, thereby recirculatingit in shunt-wise relation to the main circulation stream, andrecirculation is maintained at a rate suflicient to maintain the pH ofthe liquid withdrawn from the catholyte chamber at a predeterminedmaximum. In a typical case the liquid fed to the catholyte chamber mayhave a pH of about 7.2 and the pH of the liquid withdrawn from thecatholyte chamber will necessarily be higher. It may be restored toapproximately 7.2 by the addition thereto of anolyte liquid (having aconcentration of between 1.0 and 1.2, for example) and the recirculationof the catholyte liquid in shunt-wise relation to the main circulationstream is then maintained at a rate so that the liquid withdrawn fromthe catholyte chamber will have a pH not exceeding, in a typical case,7.5 to 8.3.

The preferred range of pH of the catholyte feed liquid is about 6.2 to8.0 andthe difference in the pH of the liquids fed to and withdrawn fromthe catholyte chamber is preferably not more than about 1.5.

When the manganese concentration is used as the criterion for the rateof recirculation of catholyte, the pH of the catholyte may be maintainedwithin the limits named, that is, the maintenance of the manganeseconcentration within thelimits named will also maintain the pH withinthe limits named, respectively.

In like manner, the pH or acid concentration in the anolyte liquid maybe controlled and in accordance with the present invention there iscontinuously fed to the anolyte chamber anolyte liquid having apredetermined minimum cohcentration of hydrogen ion. There iscontinuously withdrawn from the. anolyte chamber anolyte liquid having ahydrogen ion concentration greater than that of the liquid fed to saidanolyte chamber because of the electrolytic changes occurring therein.This acid concentration is reduced to approximately that of the anolytefeed liquid. This may be done in the anolyte chamber prior to thewithdrawal of anolyte liquid by transfer of catholyte liquid to theanolyte within the cell or by withdrawal of catholyte liquid from thecell and addition thereof to the recirculated anolyte liquid, or bothmethods of decreasing the acid concentration of the anolyte liquid maybe employed. It may be pointed out here that fundamentally the source ofthe hydroxyl ion for accomplishing this partial neutralization orreduction in acid concentration is the ore. The ore is treated withanolyte liquid to generate catholyte liquid from which the manganese isdeposited on the cathode and as a result of thechemical changesoccurring in the treatment of the ore with the anolyte liquid and theelectrolytic changes occurring in the catholyte chamber the catholyteliquid has an alkalinity which is utilized in this invention to controlthe acid concentration of the recirculated anolyte. Having changed theacid concentration of the liquid withdrawn from the anolyte chamberapproximately to that of the anolyte feed the said withdrawn liquid isreturned to the anolyte chamber and thereby recirculated in shunt-wiserelation to the main circulation stream and the recirculation ismaintained at a rate which is sufilcient to maintain in the liquidwithdrawn from the anolyte chamber a predetermined maximum acidconcentration or minimum pH. This provides a means of maintaining theacid concentration of the anolyte liquid within predetermined fixedlimits and in a typical case these limits may be within the range offrom 1.0 to 1.2.

The preferred acid concentration of the anolyte feed liquid correspondsto about 1.0 to 2.0 and the maximum preferred difierence in the pH ofthe liquid fed to and withdrawn from the anolyte chamber is about 1.0.

It is desirable also in many cases to control the temperature oi therecirculated catholyte and anolyte liquid and said recirculation makesit possible to effect a very close temperature con-' trol, as forexample, by introducing heat exchangers or other suitable controldevices in the recirculation circuits.

As stated at the beginning, one of the great advantages of manganeseelectrowinning is the production of manganese in extremely pure'form. Inaccordance with the present invention the catholyte liquid is generatedby treating a suitable conditioned ore or other manganese compound withanolyte liquid and the catholyte liquid so generated is then subjectedto a high degree of purification before use so as to free it fromimpurities including metals other than manganese, which would tend tocontaminate the deposit and produce undesirable electrolytic effects.

In accordance with the present invention not only is this extensivepurification effected before it is used, but there is also providedmeans for continuous purification of the catholyte liquid as a result ofthe recirculation. Even though the lytic changes.

catholyte liquid is extensively purified before use, impurities arenevertheless inevitably introduced and the introduction oi theseimpurities is cumulative because substantially nothing is removed fromthe cell except deposited manganese and the volatile products ofelectrolysis. Therefore, although the catholyte liquid may beextensively purified before use substantial concentrations of impuritiesnecessarily build up during the long periods of time which are desirablein successful commercial operation of manganese electrowinningprocesses.

The present invention provides means to prevent this occurrence-and inaccordance therewith continuous purification of the catholyte iseffected. This may be accomplished by interposing a suitable device suchas a filter in the recirculation circuit to remove impurities which mayhave separated in suspended form as a result of electro- In some cases,if desired, the recirculated catholyte liquid may be submitted totreatment with chemical agents to effect the precipitation of solubleimpurities.

Not only may the catholyte be continuously purified but similarpurification methods may be applied to the recirculated anolyte.

The principles of the invention will be defined in the claims ultimatelyappended hereto and will be further described and illustrated by thefollowing description taken in conjunction with the accompanying drawingshowing diagrammatically a form of apparatus which may be employed topractice the process of the invention.

The cell for the electrowinning of manganese is shown diagrammaticallyas provided with an anode l and a cathode 2 separated by a diaphragm 3.In practice the cell is provided with a series of cathodes and anodesarranged alternately in a row, each cathode and anode being separated bya diaphragm. The cathodes and anodes are, respectively, electricallyconnected in parallel and supplied with current at a density sufficientto accomplish the desired rate of manganese deposition. The tank 4provides a means for accumulating anolyte liquid withdrawn from theanolyte chamber 5 through the line 6, and the tank 1 serves as a sourceof anolyte feed liquid. Lines 8, 9 and I are provided for therecirculation of anolyte liquid. In the line 8 there may be interposed afilter or other purification device Ii and a heat exchanger or othertemperature control device l2. Line I3 is provided to divert a portionof the anolyte liquid to a digester H. Suitable pumps are provided toafford the necessary recirculation and movement of liquid. The digesterIt provides means for mixing anolyte liquid with a suitable conditionedmanganese ore or other suitable source of manganese. Tanks i and itprovide means of effecting successive purification of the catholyteliquid produced in the digester and a filter I1 is interposed betweenthese tanks. Tanks l8 and is provide sources of the necessary reagentsfor effecting these purifications. A line 20 conveys purified catholyteliquid from the second purificat'ion tank It to a catholyte feed storagetank 22 and in this line there is interposed a filter 23. Tank 24 servesto accumulate catholyte liquid withdrawn from the catholyte chamber 5A.Line 25 is provided to convey catholyte liquid from tank 24 to acatholyte adjustment tank 28. Line 25A is provided to convey liquid fromcatholyte adjustment tank 28 to catholyte feed tank 29 and in this linefilter 28 and temperature control device 21 are interposed. Tank 28serves as an accumulator for catholyte feed liquid to be fed to thecatholyte chamber IA. It will be understood that the necessary pumps areprovided for the recirculation and conveyance of liquids as shown anddescribed. Line II, provided with valve II, enables catholyte from tank2| to be added to anolyte in tank 4 and line 25 provided with valve llenables anolyte from tank 4 to be added to catholyte in tank 20.

The following description will serve as an illustration of one of thenumerous embodiments of the process of the invention. The cell isprovided with catholyte containing 35 grams per liter of manganese asmanganese sulfate or other soluble salt of manganese and 150 grams perliter of ammonium sulfate or other ammonium salt and with anolyte havinga concentration of 5 to 15 grams of manganese per liter as manganesesulfate or other solid salt of manganese and 150 grams per liter ofammonium sulfate or other ammonium salt. The pH of the catholyte isadjusted to about 7.2 and that of the anolyte to about 1.2. Thetemperature of the catholyte and anolyte is adjusted to about 32 C.

Current is passed through the anolyte and catholyte at a densitysufficient to deposit manganese on the cathode at a rate of about 2grams of manganese per liter per minute. This may be accomplished by acurrent density of 32 amperes per square foot at the cathode and '120amperes per square foot at the anode. Anolyte is continuously withdrawnfrom the chamber 5 and recirculated in shunt-wise relation to the maincirculation stream through line 8, tank 4, line 8, filter ll,temperature control device l2, inlet feed tank I, lines s and I0 and isfed to the anolyte chamber continuously at a pH of 1.2. Catholyte liquidfrom the chamber !A is mixed with the anolyte liquid so that the acidconcentration of the anolyte liquid in the anolyte tank l is restored toabout 1.2 to compensate for the increase in acidity caused byelectrolytic changes in the anolyte chamber. This addition of catholyteliquid to anolyte may occur by passing catholyte through the said line3|! provided with valve ii. The recirculation of the anolyte liquid fromthe anolyte tank 4 through lines 8, 9 and I0 is then maintained at arate sufilcient to maintain in the anolyte liquid withdrawn through theline 8 a pH not less than about 0.8 to 1.0.

A portion of the recirculated anolyte liquid is diverted through theline i3 mixed in a digester H with a suitable ore, e. g., rodocrosite,which is a manganese carbonate ore. The insoluble material is settledout and the supernatant liquid, which is an impure manganese sulfatesolution containing iron, cobalt, arsenic and nickel among theimpurities and having a pH of about 5, is delivered to the firstpurification tank I5 where it is treated with lime and blown with air toprecipitate iron in the form of ferric hydroxide. The precipitate isremoved in filter l1 and the filtrate treated in the second purificationtank It with ammonium sulfide from the tank is to precipitate nickel andcobalt as sulfide which are removed in the filter 23 from which thefiltrate passes through the line 20 to the manganese feed storage tank22. The proportions of anolyte liquid and ore used in the digester andthe concentrations and proportions of the purifying reagents are soadjusted as to produce in the feed storage tank 22 a purified solutioncontaining gan'ese as manganese sulfate, per liter, a preferred rangebeing 35 to 60.

From the catholyte feed tank 29 catholyte liquid is continuously fed tothe catholyte chamher, said liquid having a concentration of manganese',as manganese sulfate, of about 35 grams per liter and a pH of about 7.2.Catholyte liquid is continuously withdrawn to the catholyte tank 24 andas a result of electrolytic changes occurring in the catholyte liquidthe concentration of manganese therein is less than that of thecatholyte feed and the pH is greater than that of the catholyte feed.The liquid so withdrawn is passed to the catholyte adjustment tank 26where the concentration of manganese is increased by additions from thetank 22, to about 35 grams of manganese as manganesesulfate, per liter,and the pH is reduced by additions of anolyte liquid from the tank 4 toabout 7.2. The catholyte liquid, thus adjusted, is then passed throughfilter 26 to remove insoluble impurities or precipitates, then throughtemperature control device 21 to control the temperature to about 32(3., then to catholyte feed tank 29 and thence to the catholyte chamberand is thus recirculated in shunt-wise relation to the main circulationstream, and this recirculation is maintained at the rate of 2 liters perminute. By this means the concentration of manganese in the liquidwithdrawn from the catholyte chamber is maintained at about 34 grams perliter. At the same time this rate of recirculation will maintain a pH inthe liquid withdrawn from the catholyte chamber of 7.5 to 8.3.

The removal of insoluble impurities r precipitates from the anolyte andcatholyte, respectively, can occur continuously or intermittently bymeans of the filters II and 26 or other suitable puriflcation devices,and is of substantial valu in maintaining the purity of the electrolytesand the purity of the manganese deposit.

The over-all cell voltage is adjusted to provide a cathode drop of notless than 1.46 to 1.50 volts as measured by any suitable potentiometricmeasurin device. Having fixed the said overall voltage and the cathodepotential drop and having also fixed, in accordance with the presentinvention, the pH and composition of the catholyte and anolyte and thetemperature thereof within the prescribed limits, it will be found thatthe critical cathode potential drop will be maintained at not less thanthe values stated and a satisfactory manganese deposition will occurover long periods of time.

What we claim is:

1. In a, cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of manganesesalt in the catholyte liquid which comprises passing current through theanolyte and catholyte electrolyte at a density sufllcient to removemanganese from the catholyte and deposit it on the cathode at apredemined rate in terms of grams per liter per minute; continuouslyfeeding, to the catholyte chamber, catholyte feed liquid having apredetermined maximum concentration of manganese in the form of asoluble salt thereof; continuously withdrawing, from the catholytechamber, catholyte liquid having less manganese per liter than theliquid fed to said chamber; restoring the concentration of manganese insaid withdrawn liquid to about that of the feed liquid;

, returning said withdrawn liquid to the catholyte plenished electrolyteto the catholyte chamber th estabhshlng a main circulation stream ofelectrolyte, the method of controlling the concentration of manganesesalt in the catholyte liquid which comprises passing current through theanolyte and catholyte electrolyte at a density sufiicient to removemanganese rrom the catholyte and deposit it on the cathode at apredetermined rate in terms of grams per liter per minute; continuouslyfeeding, to the catholyte chamber, catholyte feed liquid having apredeteimined maximum concentration of manganese in the .form ofmanganese sulfate; continuously withdrawing, from the catholyte chamber,catholyte liquid having less manganese per liter than the liquid fed tosaid chamber; restoring the concentration of manganese in said withdrawnliquid to about that of the feed liquid; returning said withdrawn liquidto the catholyte chamber and thereby recirculating it in shuntwiserelation to the main circulation stream, and maintaining therecirculation at a rate sufficient to maintain in the liquid withdrawnfrom the catholyte chamber a predetermined minimum concentration ofmanganese.

3. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of manganesesalt in the catholyte liquid which comprises passing current through theanolyte and catholyte at a density sufliclent to remove manganese fromthe catholyte and deposit it on the cathode at a rate of about 0.25 to2.00 grams per liter per minute; continuously feeding, to the catholytechamber, catholyte feed liquid having a predetermined maximumconcentration of manganese in the form of a soluble salt thereof;continuously withdrawing, from the catholyte chamber, catholyte liquidhaving less manganese per liter than the liquid fed to said chamber;restoring the concentration of manganese in said withdrawn liquid toabout that of the feed liquid; returning said withdrawn liquid to thecatholyte chamber and thereby recirculating it in shunt-wise relation tothe main circulation stream, and maintaining the recirculation at a ratesuiflcient to maintain in the liquid withdrawn from the catholytechamber a predetermined minimum concentration of manganese. 4. In acyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replemshment ofmanganesee therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of manganesesalt in the catholyte liquid which comprises passing current through theanolyte and catholyte at a density sumcient to remove manganese from thecatholyte and deposit it on the cathode at a rate of about 0.25 to 2.00vgrams per liter per minute; continuously feeding, to the catholytechamber, catholyte feed liquid having a predetermined maximumconcentration of manganese in the form of manganese sulfate;continuously withdrawing, from the catholyte chamber, catholyte liquidhaving less manganese per liter than the liquid fed to said chamber;restoring the concentration of manganese in said withdrawn liquid toabout that of the feed liquid by the addition of replenished electrolytefrom the main circulation stream; returning said withdrawn liquid to thecatholyte chamber and thereby recirculating it in shunt-wise relation tothe main circulation stream, and maintaining the recirculation at a ratesuflicient to maintain in the liquid withdrawn from the catholytechamber a predetermined minimum concentration of manganese.

5. A method of controlling the concentration of manganese salt in thecatholyte liquid, which comprises passing current through the anolyteand catholyte at a density sufficient to remove manganese from thecatholyte and deposit it on the cathode at a rate of about 0.25 to 2.00grams per liter per minute; continuously feeding, to the catholytechamber, catholyte feed liquid having a maximum concentration of about25 to 50 grams of manganese in the form of a soluble salt thereof;continuously withdrawing, from the catholyte chamber, catholyte liquidhaving less manganese per liter than the liquid fed to said chamber;restoring the concentration of manganese in said withdrawn liquid toabout that of the feed liquid; returning said withdrawn liquid to thecatholyte chamber and thereby recirculating it in shunt-wise relation tothe main circulation stream, and maintaining the recirculation at a ratesufficient to maintain in the liquid withdrawn from the catholytechamber a predetermined -minimum concentration of manganese, thedifference in concentration of manganese in the liquids fed to andwithdrawn from the catholyte chamber, respectively, being not more thanabout 15 grams of manganese per liter.

6. A method of controlling the concentration of manganese salt in thecatholyte liquid, which comprises passing urrent through the anolyte andcatholyte at density suflicient to remove manganese from the catholyteand deposit it on the cathode at a rate of about 0.25 to 2.00 grams perliter per minute; continuously feeding, to the catholyte chamber,catholyte feed liquid having a maximum concentration of about 25 to 50grams of manganese in the form of manganese sulfate; continuouslywithdrawing, from the catholyte chamber, catholyte liquid having lessmanganese per liter than the liquid fed to said chamber; restoring theconcentration of manganese in said withdrawn liquid to about that of thefeed liquid; returning said withdrawn liquid to the catholyte chamberand thereby recirculating it in shunt-wise relation to the maincirculation stream, and maintaining the recirculation at a ratesufficient to maintain in the liquid withdrawn from the catholytechamber a predetermined minimum concentration of manganese, thedifference in concentration of manganese in the liquids fed to andwithdrawn from the catholyte chamber, respectively, being not more thanabout 15 grams oi manganese per liter.

7. In a cyclic process for the clectrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition oisaid replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of acid in theanolyte liquid which comprises passing current through the anolyte andcatholyte at a density sufllcient to generate hydrogen ion in theanolyte at a predetermined rate in terms of grams of hydrogen ion perliter per minute; continuously feeding to the anolyte chamber anolytefeed liquid having a predetermined minimum acid concentration;continuously withdrawing from the anolyte chamber anolyte liquid havinga concentration of hydrogen ion greater than that of the liquid fed tosaid anolyte chamber; reducing the concentration of acid in said anolyteliquid to about that of the feed liquid; returning said withdrawn liquidhaving said reduced acid concentration to the anolyte chamber andthereby recirculating it in shunt-wise relation to the main circulationstream; and maintaining the recirculation of the anolyte liquid at arate sumcient to maintain in the liquid withdrawn from the anolytechamber a predetermined maximum acid concentration.

8. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of acid in theanolyte liquid which comprises passing current through the anolyte andcatholyte at a density suflicient to generate hydrogen ion in theanolyte at a predetermined rate in terms of grams of hydrogen ion perliter per minute; continuously feeding to the anolyte chamber anolytefeed liquid having a minimum acid concentration corresponding to a pH ofabout 1.0 to 2.0; continuously with.. drawing from the anolyte chamberanolyte liquid having an acid concentration greater than that of theliquid fed to said anolyte chamber; reducing the concentration of acidin said anolyte liquid to about that of the. feed liquid; returning saidwithdrawn liquid having said reduced acid concentration to the anolytechamber and thereby recirculating it in shunt-wise relation to the maincirculation stream; and maintaining the recirculation of the anolyteliquid at a rate sufflcient to maintain in the liquid withdrawn from9,361,148 the anolyte chamber a predetermined maximum acidconcentration, the diiference in th pH of the liquids fed to andwithdrawn from the anolyte chamber being not greater than about 1.0.

9. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of acid in theanolyte liquid which comprises passing current through the Y anolyte andcatholyte at a density suflicient to generate hydrogen ion in theanolyte at a predetermined rate in terms of grams of hydrogen ion perliter per minute; continuously feeding to the anolyte chamber anolytefeed liquid having a predetermined minimum acid concentration; divertinga portion of said anolyte liquid; mixing said diverted anolyte liquidwith a manganese compound soluble therein to generate catholyte liquidwhereby the acid in the anolyte liquid is neutralized, the pH thereofincreased and the concentration of manganese increased; continuouslywithdrawing from the anolyte chamber anolyte liquid having an acidconcentration greater than that of the liquid fed to said anolytechamber; reducing the concentration of acid in said anolyte liquid toabout that of the feed liquid by the addition thereto of catholyteliquid; returning said withdrawn liquid having said reduced acidconcentration to the anolyte chamber and thereby recirculating it inshunt-wise relation to the main circulation stream, and maintaining therecirculation of the anolyte liquid at a rate sufilcient to maintain inthe liquid withdrawn from the anolyte chamber a predetermined maximumacid concentration.

10. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thcatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the concentration of acid in theanolyte liquid which comprises passing current through the anolyte andcatholyte at a density suilicient to generate hydrogen ion in theanolyte at a predetermined rate in terms 01' grams of hydrogen ion perliter per minute; continuously feeding to the anolyte chamber anolytefeed liquid having a minimum acid concentration corresponding to a pH oiabout 1.0 to 2.0; diverting a portion of said anolyte liquid; mixingsaid diverted anolyte liquid with a manganese compound soluble thereinto generate catholyte liquid whereby the acid in the anolyte liquid isneutralized, the pH thereof increased and the concentration of manganeseincreased; continuously withdrawing from the anolyte chamber anolyteliquid having an acid concentration greater than that of the liquid fedto said anolyte chamber; reducing the concentration of acid in saidanolyte liquid to about that of the feed liquid by the addition theretoof catholyte liquid; returning said withdrawn liquid havingsaid reducedacid concentration to in shunt-wise relation to the main circulationstream, and maintaining the recirculation of the anolyte liquid at arate sufficient to maintain in the liquid withdrawn from the anolytechamber a predetermined maximum acid concentration, the diflerence inthe pH of the liquids fed to and withdrawn from the anolyte chamberbeing not reater than about 1.0.

11. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thcatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the pH in the catholyte liquidwhich comprises. passing current through the anolyte and catholyte at adensity sumcient to remove manganese from the catholyte and deposit iton the cathode at a predetermined rate in terms of grams per liter perminute as a result of which the pH of the catholyte is increased;continuously feeding to the catholyte chamber catholyte feed liquidhaving a predetermined pH; continuously withdrawing from the catholytechamber catholyte liquid having a higher pH than that of the liquid fedto said chamber; reducing the pH in said withdrawn catholyte liquid toabout that of the feed liquid; returning said withdrawn liquid havingsaid reduced pH to the catholyte chamber and thereby recirculating it inshunt-wise relation to the main circulation stream, and maintaing therecirculation of said catholyte liquid at a rate sumcient to maintain inthe liquid withdrawn from the catholyte chamber a predetermined maximumpH.

12. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and. anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thcatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controllin the pH in the catholyte liquidwhich comprises passing current through the anolyte and catholyte at adensity suillcient to remove manganese from the catholyte and deposit iton the cathode at a predetermined rate in terms of grams per liter perminute as a result of which the pH of the catholyte is increased;continuously feeding to the catholyte chamber catholyte feed liquidhaving a predetermined pH; continuously withdrawing from the catholytechamber catholyte liquid having a higher pH than that of the liquid fed.to said chamber; reducing'the pH in said withdrawn catholyte liquid toabout that of the feed liquid by adding anolyte liquid thereto;returning said withdrawn liquid having said re duced pH to the catholytechamber and thereby recirculating it in shunt-wise relation to the maincirculation stream, and maintaining the recirculation of said catholyteliquid at a rate sufflcient to maintain in the liquid withdrawn from thecatholyte chamber a predetermined maximum pH.

13. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell dithe anolyte chamber and thereby recirculating itvided into catholyteand anolyte chambers containing catholyte andanolyte, respectively, said cyclic process comprising the withdrawal ofanolyte liquid from the anolyte chamber, replenishment of manganesetherein and addition of said replenished electrolyte to the catholytechamber thus establishing a main circulation stream of electrolyte, themethod oi controlling the pH in the catholyte liquid which comprisespassing current through the anolyte and catholyte at a densitysuillcient to remove manganese from the catholyte and deposit it on thecathode at a predetermined rate in terms oi grams per liter per minuteasa result of which the pH of the catholyte is increased; continuouslyfeeding to the catholyte chamber catholyte feed liquid having apredetermined pH of about 6.2 to 8.0; continuously withdrawing from thecatholyte chamber catholyte liquid having a higher pH than that of theliquid fed to said chamber; reducing the pH in said withdrawn catholyteliquid to about that of the feed liquid; returning said withdrawn liquidhaving said reduced pH to the catholyte chamber and therebyrecirculating it in shunt-wise relation to the main circulation stream,and maintaining the recirculation of said catholyte liquid at a ratesuillcient to maintain in the liquid withdrawn from the catholytechamber a predetermined maximum pH, the difference in the pH of theliquid fed to and withdrawn from the catholyte chamber being not morethan about 1.5.

14. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the pH in the catholyte liquidwhich comprises passing current through the anolyte and catholyte at adensity suificient to remove manganese from the catholyte and deposit iton the cathode at a predetermined rate in terms of grams per liter perminute as a result of which the pH of the catholyte is increased;continuously feeding to the catholyte chamber catholyte feed liquidhaving a pH of about 6.2 to 8.0; continuously withdrawing from thecatholyte chamber catholyte liquid having a higher pH than that of theliquid fed to said chamber; reducing the pH in said withdrawn catholyteliquid to about that of the feed liquid by adding anolyte liquidthereto; returning said withdrawn liquid having said reduced pH to thecatholyte chamber and thereby recirculating it in-shunt-wise relation tothe main circulation stream, and maintaining the recirculation of saidcatholyte liquid at a rate sumcient to maintain in the liquid withdrawnfrom the stream of electrolyte, the method of controlllns thecomposition and acid concentration of the electrolytes which comprisespassing current through the anolyte and catholyte at a densitysuflicient to remove managanese from the catholyte and deposit it on thecathode at a predetermined ratein terms 01' grams of manganese per literper minute continuously eeding to the catholyte chamber catholyte feedliquid having a predetermined maximum concentration or manganese in theform of a soluble salt thereof; continuously withdrawing, from thecatholyte chamber, catholyte liquid having less manganese per liter thanthe liquid fed to said chamber; re storing the concentration ofmanganese in said withdrawn liq id to about that of the feed liquid;returning said withdrawal liquid and thereby recirculating it inshunt-wise relation to the main circulation stream; maintaining therecirculation at a rate suflicient to maintain in the liquid withdrawnfrom the catholyte chamber a predetermined minimum concentration ofmanganese; continuously feeding to the anolyte chamber anolyte i'eedliquid having a predetermined minimum acid concentration; continuouslywithdrawing from the anolyte chamber anolyte liquid having an acidconcentration'greater than that of the liquid fed to said anolytechamber; reducing the concentration of acid in said anolyte liquid toabout that of the feed liquid; returning said withdrawn liquid havingsaid reduced acid concentration to the anolyte chamber and therebyrecirculating it separately from the main circulation stream, andmaintaining the recirculation of the anolyte liquid at a rate suflicientto maintain in the liquid withdrawn from the anolyte chamber apredetermined maximum acid concentration.

16. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprisng thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the composition and acidconcentration of the electrolytes which comprises passing currentthrough the anolyte and catholyte at a density suflicient to removemanganese from the catholyte and deposit it on the cathode at a rate ofabout 0.25 to 2.00 grams of manganese per liter per minute; continuouslyfeeding to the catholyte chamber catholyte feed liquid having apredetermined maximum concentration of about 25 to 50 grams of manganesein the form of manganese sulfate;

' cont nuously withdrawing, from the catholyte catholyte chamber apredetermined maximum chamberfcatholyte liquid having less manganese perliter than the liquid fed to said chamber; restoring the concentrationof manganese in said withdrawn l quid to about that of the feed liquid;return ng said withdrawn liquid and thereby recirculating it inshunt-wise relation to the main circulation stream; maintaining therecirculation at a rate sufllcient to maintain in the liquid withdrawnfrom the catholyte chamber a predetermined minimum concentration ofmanganese, the difference in concentration of manganese in the liquidsfed to and withdrawn from the catholyte chamber, respectively, being notmore than about 15 grams of manganese per liter; continuously feeding tothe anolyte chamber anolyte feed liquid having a minimum acidconcentration corassures responding to a pH of about 1.0 to 2.0;continuously withdrawing from the anolyte chamber anolyte liquid havingan acid concentration greater than that of the liquid fed to saidanolyte chamber; reducing the concentration of acid in acid anolyteliquid to about that of the feed liquid; returning said withdrawn liquidhaving said reduced acid concentration to the anolyte chamber andthereby recirculating it separately from the main circulation stream,and maintaining th recirculation of the anolyte liquid at a ratesuflicient to maintain in the liquid withdrawn from the anolyte chambera predetermined maximum acid concentration, the difference in the pH ofthe liquids fed to and withdrawn from the anolyte chamber being notgreater than about 1.0.

17. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the composition and acidconcentration of the electrolytes which comprises passing currentthrough the anolyte and catholyte at a density sufflcient to removemanganese from the catholyte and deposit it on the cathode at apredetermined rate in terms of grams of manganese per liter per -minute;continuously feeding to the catholyte chamber catholyte feed liquidhaving a predetermined maximum concentration of manganese in the form ofa soluble salt thereof; continuously withdrawing, from the catholytechamber, catholyte liquid having less manganese per liter than theliquid fed to said chamber; restoring the concentration of manganese insaid withdrawn liquid to about that of the feed liquid; returning saidwithdrawn liquid and thereby recirculating it in shunt-wise relation tothe main circulation stream; maintaining the recirculation at a ratesuflicient to maintain in the liquid withdrawn from the catholytechamber a predetermined minimum concentration of manganese; continuouslyfeeding to the anolyte chamber anolyte feed liquid having a,predetermined minimum acid concentration; diverting a portion of saidanolyte liquid; mixing said diverted anolyte liquid with a manganesecompound soluble therein to generate catholyte feed liquid whereby theacid in the anolyte liquid is neutralized, the pH thereof increased andthe concentration of manganese increased; continuously withdrawing fromthe anolyte chamber anolyte liquid having an acid concentration greaterthan that of the liquid fed to said anolyte chamber; reducing theconcentration of acid in said anolyt liquid to about that of the feedliquid; returning said withdrawn liquid having said reduced acidconcentraton to the anolyte chamber and thereby recirculating itseparately from the main circulation stream, and maintaining therecirculation of the anolyte liquid at a rate sufiicient to maintain inthe liquid withdrawn from the anolyte chamber a predetermined maximumacid concentration.

18. In a cyclic-process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, re-

chamber thus establishing a main circulation stream of electrolyte, themethod of controlling the composition and acid concentration of theelectrolytes which comprises passing current through the anolyte andcatholyte at a density sufficient to remove manganese from the catholyteand deposit it on the cathode at a rate 0! about 0.25 to 2.00 grams ofmanganese per liter per minute; continuously feeding'to the catholytechamber catholyte feed liquid having a predetermined maximumconcentration of about 25 to 50 grams of manganese in the form ofmanganese sulfate; continuously withdrawing, from the catholyte chamber,catholyte liquid having less manganese per liter than the liquid fed tosaid chamber; restoring the concentration of manganese in said withdrawnliquid to about that of the feed liquid; returning said withdrawn liquidand thereby recirculating it in shunt-wise relation to the maincirculation stream; maintaining the recirculation at a rate suflicientto maintain in the liquid withdrawn from the catholyte chamber apredetermined minimum concentration of manganese, the difference inconcentration of manganese in the liquids fed to and withdrawn from thecatholyte chamber, respectively, being not greater than about 15 gramsof manganese per liter; continuously feeding to the anolyte chamberanolyte feed liquid having a minimum acid concentration corresponding toa pH of about 1.0 to 2.0; diverting a portion of said anolyte liquid;mixing said diverted anolyte liquid with a manganese compound solubletherein to generate catholyte feed liquid whereby the acid in theanolyte liquid is neutralized, the pH thereof increased and theconcentration of manganese increased; continuously withdrawing from theanolyte chamber anolyte liquid having an acid concentration greater thanthat of the liquid fed to said anolyte chamber; reducing theconcentration of acid in said anolyte liquid to about that of the feedliquid; returning said withdrawn liquid having said reduced acidconcentration to the anolyte chamber and thereby recirculating itseparately from the main circulation stream, and maintaining therecirculation of the anolyte liquid at a rate suflicient to maintain inthe liquid withdrawn from the anolyte chamber a predetermined maximumacid concentration, the difference in the pH of the liquids fed to andwithdrawn from the anolyte chamber being not more than about 1.0.

19. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell divided into catholyte and anolyte chambers containingcatholyte and anolyte, respectively, said cyclic process comprising thewithdrawal of anolyte liquid from the anolyte chamber, replenishment ofmanganese therein and addition of said replenished electrolyte to thecatholyte chamber thus establishing a main circulation stream ofelectrolyte, the method of controlling the composition and acidconcentration of the electrolytes which comprises passing currentthrough the anolyte and catholyte at a density suflicient to removemanganese from the catholyte and deposit it on the cathode at apredetermined rate in terms of grains of manganese per liter per minute;continuously feeding to the catholyte chamber catholyte feed liquidhaving a predetermined maximum concentration of manganese in the form ofa soluble salt thereof; continuously withdrawing, from the catholytechamber, catholyte liquid having less manganese per liter than theliquid fed to said chamber; restoring the concentration of manganese insaid withdrawn liquid to about that of the feed liquid; returning saidwithdrawn liquid and thereby recirculating itin shunt-Wise relation tothe main circulation stream; maintaining the recirculation at a ratesumcient to maintain in the liquid withdrawn from the catholyte chambera predetermined minimum concentration of manganese; removing insolubleimpurities from the recirculated liquid; continuously feeding to theanolyte chamber anolyte feed liquid having a predetermined minimum acidconcentration; diverting a portion of said anolyte liquid; mixing saiddiverted anolyte liqlyte and catholyte at a density sumcient to removemanganese from the catholyte and deposit it on the cathode at apredetermined rate in uld with a manganese compound soluble therein togenerate catholyte feed liquid whereby the acid in the anolyte liquid isneutralized, the pH thereof increased and the concentration of manganeseincreased; continuously withdrawing from the anolyte chamber anolyteliquid having an acid concentration greater than that of the liquid fedto said anolyte chamber; reducing the concentration of acid in saidanolyte liquid to about that of the feed liquid by the addition ofcatholyte; returning said withdrawn liquid having said reduced acidconcentration to the anolyte chamber and thereby recirculating itseparately from the main circulation stream, and maintaining therecirculation of the anolyte liquid at a rate sufficient to maintain inthe liquid withdrawn from the anolyte chamber a predetermined maximum.

20. In a cyclic process for the electrowinning of manganese employing anelectrolytic cell diterms of gramsot manganese per liter per minute;continuously feeding to the catholyte chamber catholyte teed liquidhaving a predetermined maximum concentration of manganese in the form ofa soluble salt thereof; continuously withdrawing, from the catholytechamber, catholyte liquid having less manganese per liter than theliquid fed to said chamber; restoring the con centration of manganese insaid withdrawn liquid to about that of the feed liquid; returning saidwithdrawn liquid and thereby recirculating it in shunt-wise relation tothe main circulation stream; maintaining the recirculation at a ratesufficient to maintain in the liquid withdrawn from the catholytechamber a predetermined minimum concentration of manganese: continuouslyfeeding to the anolyte chamber anolyte teed liquid having apredetermined minimum acid concentration; diverting a portion of saidanolyte liquid; mixing said diverted anolyte liquid with a manganesecompound soluble therein to generate catholyte liquid whereby the acidin the anolyte liquid is neutralized, the pH thereof increased and theconcentration of manganese increased: continuously withdrawing from theanolyte chamber anolyte liquid having an acid concentration greater thanthat of the liquid fed to said anolyte chamber; reducing theconcentration of acid in said anolyte liquid to about that of the feedliquid by the addition of catholyte; returning said withdrawn liquidhaving said reduced acid concentration to the anolyte chamber andthereby recirculating it separately from the main circulation stream;removing insoluble impurities from the recirculated liquid, andmaintaining the recirculation of the anolyte liquid at a rate sufficientto maintain in the liquid withdrawn from the anolyte chamber apredetermined maximum.

KARL M. LEUTE.

CHARLES L. MANTEU...

WILLIAM L. HAMMERQUIST.

